Charles elterich



(No Model.)

0 ELT'ERIGH.

TAP.

Patented May 5, 1896.

, INVENTOR WlINSSES Nrrnn STATES f ATENT OFFICE.

CHARLES ELTERICILOF NEIV YORK, N. Y.

TAP.

SPECIFICATION forming part of Letters Patent No. 559,372, dated May 5,1896.

Application filed June 2 8, 1 8 9 5 T at whom, it may concern.-

Be it known that 1, CHARLES ELTERICH, a citizen of the United States ofAmerica, residing at New York, in the county and State of New York, haveinvented certain new and useful Improvements in Taps, of which thefollowing is a specification.

My invention has reference to improvements intaps for cutting internalor female screw-threads, and has for its object to provide a tap adaptedsingly for the purpose of cutting a perfect continuous thread of anydesired length. To this end I construct the tap with a continuous threadconsisting of alternate taper and straight portions, the straightportions increasing in diameter toward the shank, while the diameter ofthe bottom of the thread is substantially uniform from beginning to end.

I'Ieretofore tapshave been constructed with two or more threadedsections of different diameters, each section having a uniform diameterthroughout its length; but in every instance the diameter of the bottomof the thread increases with the increased diameter of the apex of thethread.

The main feature of my invention consists, therefore, in having thediameter at the bottom of the thread uniform throughout the length ofthe tap.

The known taps, asabove described, have also usually been formed withclearingspaces between the several sections, which spaces I omit, and soincrease the strength of the tap and avoid clogging.

The nature of my invention will best be understood when described inconnection with the accompanying drawings, in which- Figure 1 is adiagrammatic exaggerated view illustrating the principle on which thetap is constructed. Fig. 2 is an elevation of the tap as constructed inpractice. Fig. 3 is a section on the line 3 3, Fig. 2.

Similar letters and figures of reference designate corresponding partsthroughout the several views of the drawings.

Referring at present to Fig. 1, I shall proceed to describe the mannerof construction of the tap, which is as follows: A suitablyturned steelrod is first cut with a parallel thread extending from one end to theother. At the extreme end of the tap the thread is tapered for a shortdistance, as at a, between lines 1 and 2, the bottom. of which taper-Serial No. 554,288. (No model.)

bottom of the thread a. The thread is then reduced and cut taper betweenthe lines 1 2 and 2 3, for the purpose of facilitating the entering ofthe tap and the cutting. The section 3 4 is then reduced cylindrical orstraight, the section 4 5 is reduced to an abrupt taper, section 5 6 isreduced parallel and of greater diameter than section 3 4, and so on,until finally the finishing thread section 7 8 is reached, which latteris left in its original condition. y The bottom of the thread istherefore uniform throughout with the exception of the extreme end ofthe tap, where it is reduced for the purpose above mentioned. Thefinished tap therefore consists of a reduced end or point, a series ofreduced alternating straight and tapered portions 1) c, and a fin--ishing portion Z). with flutes d.

I have found that by having the thread continuous and of uniformdiameter at its bottom, with the exception as to its point, as abovestated, to facilitate entering, a single tap will answer for the cuttingof a perfect thread of any desired length without appreciable wear onthe tap. By forming the thread continuousgreat strength and resistingpower, a matter very essential in taps, is obtained. In practice I makethe taper portion 0 between the cylindrical or straight portions I)quite abrupt.

One of the important features of the present construction for taps isthat the thread is It is, as usual, provided finished smooth and solid,without break or ence of two witnesses.

CHAS. ELTERICH.

- Witnesses:

Enenmn A. PERSIDES, A. FABER DU FAUR, Jr.

